This research project is addressed to the question of how the visceral arches develop and how they contribute to the morphogenesis of the oro-facial complex. A basic aspect of the approach to this question is to compare and contrast the development of the embryonic landscape in the mouse and in an infrahuman primate under laboratory conditions wherein development time and specimen preparation are strictly controlled. Scanning electron microscopy with microscopy will provide surface and subsurface details of changing contours and cell differentiation. Growth equations and photogrammetric analysis in three dimensions will be used to analyze changes with time and to show differences between species at comparable stages of embryonic development.